In recent years, in the field of display apparatuses used for achieving image display on computers, televisions and the like, plasma display panels (hereinafter referred to as PDPs) have been attracting attention. This is because a PDP enables a slim and large panel demonstrating high image quality to be realized.
In a conventional PDP, a pair of a front substrate and a back substrate are arranged so as to oppose each other. Scan electrodes and sustain electrodes are disposed in stripes so as to be parallel to each other on the opposing surface of the front substrate. The scan and sustain electrodes are covered with a dielectric layer. Data electrodes are arranged in stripes on the opposing surface of the back substrate so as to cross over the scan electrodes at right angles. A gap between the front substrate and the back substrate is divided by barrier ribs which are disposed in stripes so as to be parallel to the data electrodes. A discharge gas is enclosed in spaces formed between these barrier ribs. With this structure, a plurality of discharge cells are formed, in a matrix configuration, in areas where the scan electrodes intersect with the data electrodes in the PDP.
This PDP is provided with a driving circuit, to constitute a plasma display apparatus. The PDP is driven by repeating a sequence of a set-up period, a write period, a discharge sustain period, and an erase period, which causes each of the discharge cells to be lit and unlit. In the set-up period, a set-up pulse is applied to initialize all of the discharge cells. In the write period, a data pulse is applied to selected data electrodes, while a scan pulse is sequentially applied to the scan electrodes, to write pixel information. In the discharge sustain period, a sustain pulse having a rectangular waveform is applied with alternating polarity between the scan electrodes and the sustain electrodes, to sustain a main discharge and thereby cause light emission. In the erase period, an erase pulse is applied to the scan electrodes or the sustain electrodes, to erase wall charges in the discharge cells. Here, each discharge cell is fundamentally only capable of two display states, ON and OFF. Therefore, driving is performed in plasma display apparatuses using a field timesharing gradation display method, in which one frame (field) is divided into sub-fields, and ON and OFF states in each sub-field are combined to express a gray scale.
Here, it is desirable to utilize the field timesharing gradation display method together with a technique of suppressing an erroneous discharge, such as illuminating an unselected discharge cell or failing to illuminate a selected discharge cell.
Particularly in the erase period, noise or interference generated by priming particles flowing into a discharge cell from other discharge cells tends to cause an erroneous discharge. To suppress such erroneous discharge, a pulse lower than a discharge firing voltage and narrower than the sustain pulse is applied in the erase period, to stop a sustain discharge. Such a pulse is hereinafter referred to as a “narrow pulse”.
However, an erase discharge tends to be less stable in recent plasma display apparatuses, which deliver increasingly higher definition. Accordingly, an erroneous discharge may be caused because of erase defects.
When driving an existing PDP conforming to the video graphics array (VGA) protocol, one field can be divided into around 13 sub-fields. When driving a PDP conforming to the extended graphic array (XGA), however, the number of sub-fields for one field is reduced to 8 to 10, if the lengths of the write period (1.5 ms to 1.9 ms with a write pulse of 2 μs to 2.5 μs in width) and the discharge sustain period are the same as those in the VGA. This means that lower image quality is performed in the XGA PDP than in the VGA PDP. In view of this problem, the pulse width of the sustain pulse applied in the discharge sustain period is reduced from conventional 6 μs to 4 μs, to shorten the discharge sustain period, thereby increasing the number of sub-fields. However, when the sustain pulse is narrower, a smaller wall charge accumulates in the discharge cells as a result of a sustain discharge, which lowers a wall voltage. This makes it difficult to perform an erase discharge in the erase period which follows the discharge sustain period, causing an unstable discharge in the erase period. As a result, discharges in the set-up period and write period that follow the erase period become unstable too. Accordingly, an erroneous discharge is likely to take place, causing a reduction in the image quality.
In the light of the above-mentioned problems, it is an object of the present invention to provide a plasma display apparatus, in which the narrow pulse is used to perform the erase discharge and the discharge sustain period of each sub-field can be shortened so as to achieve high definition with suppressing an erroneous discharge.